The present invention relates generally to the field of apparatus for fiber optic communication, and more particularly, to a multi-channel fiber optic rotary joint using an optical expander/condenser to achieve a compact beam structure.
A typical multiply channel fiber optic rotary joint consists of rotatable fiber collimator array, a de-rotating mechanism, and the fixed fiber collimator array all of which rotate about a common axis. The de-rotating mechanism allows the light signals applied to any one or all of a number of inputs to be reproduced at a corresponding number of outputs of the fiber optic rotary joint in a continuous manner. The de-rotating mechanism normally consists of an optical de-rotating mechanics such as a Dove prism, Delta prism, Schmidt-Pechan prism, Abbe-Konig prism, K-mirror, or GRIN lens to name a few and a passive mechanical system which rotates the optical de-rotating mechanism.
The determining factor for the size of these multi-channel fiber optic rotary joints is the size of the de-rotating mechanism which is a function of the number of beams that can be passed through the de-rotating mechanism simultaneously. The number of beams was traditionally limited by the physical size of the collimators and collimator arrays. Therefore, even in the most tightly packed beam structure would have a relatively low number of beams per square millimeter because the amount of space occupied by the collimators and collimator arrays is vastly larger than the beam size resulting in a relatively long distance between neighboring beams.
Optical expanders and optical condenser are extensively used to achieve magnification or demagnification. They are essentially telescopes or magnifying glasses which achieve their magnification or demagnification through the use of refractors.